The invention relates to pneumatic tire retreading, and more particularly to a device for sealing a tire retreading envelope against a tire carcass to prevent air leakage when the envelope is evacuated and the tread is vulcanized onto the carcass.
In tire retreading utilizing premolded, precured tire tread, the buffed tire carcass, a layer of uncured rubber compound, and the premolded tread rubber are assembled and placed into a flexible rubber envelope which encases all or a substantial portion of the carcass and the precured tread. The interior of the envelope is then substantially evacuated, and its exterior is subjected to positive pressure to hold the tire tread firmly in place while it is bonded to the tire carcass. Such a procedure and apparatus are shown, for example, in U.S. Pat. No. 3,779,830, which also discloses inflation of the tire carcass during tread replacement.
The flexible envelope must be placed about the tire in sealed relationship, which has been cumbersome, time-consuming and undependable, according to prior art procedures and apparatus. The encased tire with the preformed tread is placed in a heated chamber or autoclave for vulcanization of the tread to the tire carcass. A type of apparatus for recapping a tire and sealing the envelope closed is shown in U.S. Pat. No. 3,886,028.
One approach to the problem of sealing a tire envelope to a tire to be retreaded is shown in U.S. Pat. No. 4,274,897. Another apparatus of that provides an improved tire envelope sealing system which is superior to that disclosed in the latter patent is described in my co-pending application Ser. No. 579,437, filed Feb. 13, 1984. Although the devices shown in the aforesaid disclosures are all effective to a degree in sealing a tire envelope for a tire being retreaded, they may become inefficient where a tire with a worn or damaged bead area is encountered. In such a situation, it may be difficult to properly seal the envelope in the bead area, thereby jeopardizing the entire recapping procedure.
It is therefore one object of the present invention to solve the aforesaid problem by providing an improved apparatus for sealing a retreading envelope about a tire for recapping that applies concentrated sealing pressure in the bead.
Another object of the invention is to provide apparatus for sealing an envelope on a tire for recapping that is simple and easy to install without the need for special tools and yet highly effective so that air and other gases are more dependably prevented from entering the envelope during curing.